1. Technical Field
This invention generally relates to integrated circuits on semiconductors, and more specifically relates to scannable fuse latches on these circuits.
2. Background Art
An on-chip fuse on an integrated circuit is a device that can be permanently set. When the fuse is initially created, it is essentially a "short", meaning that there is very little or no electrical resistance from one end to the other of the fuse. The fuse may be left this value, which is a logic zero. Alternatively, the fuse may be "blown" to become a logic one. In this state, there is a very high or infinite resistance from one end to the other of the fuse. Generally, a destructive process is used to blow the fuse.
On-chip fuses are used for various reasons. One reason is to provide an identity, which can provide the manufacturer valuable information about when and where the semiconductor chip was made. Another reason is to provide configuration bits, which permanently configure the chip. A final exemplary reason is to provide "remapping" of Random Access Memory (RAM) cells. When a RAM semiconductor chip is made, more RAM cells than needed are actually made on the chip. When bad RAM cells are found through testing, the good, extra RAM cells are "remapped" so that they are used instead of the bad RAM cells. The chip is retested and this process continues until the RAM chip completes an error-free test.
While fuses provide definite benefits to integrated circuit manufacturers, designers, and failure engineers, there are problems with the current fuses and their accessing mechanisms.